Subsea connection apparatus

ABSTRACT

Subsea connection apparatus comprising: a frame ( 5 ) connectable to a subsea structure ( 1 ); docking means for connecting the frame to the subsea structure; conduit handling means ( 10 ) positioned on the frame to facilitate the positioning of a conduit for attachment to a subsea structure; and means for docking a subsea tool and/or vehicle ( 20 ) onto the frame.

[0001] The present invention is a subsea connection apparatus which canbe used to assist in the subsea connection of flexible or rigidflowlines and umbilicals or bundles (hereinafter referred to asconduits) to subsea structures.

[0002] One of the most complex and expensive tasks required to beundertaken by means of diverless intervention is that of connectingconduits to subsea structures. In order to make the connection theconduit must be manoeuvred into position at the subsea structure in acontrolled manner to ensure proper connection of the conduit to thesubsea structure. This connection can be made during conduit layingoperations by means of a vertical connection which uses a surface vesselto position the end of the conduit onto a structure connection clamp. Inthis type of On-structure deployment, vertical heave of the vessel cancause damage to the connection points on the subsea structure andconduit; this is a particular problem in stormy weather. In addition,this technique requires the use of a complicated subsea porch structureand an additional component on the end of the conduit.

[0003] Where a conduit is deployed to the seabed with an end terminationhead at some time prior to connection, the technique is called On-seabedconnection. In such cases, the conduit is pulled to the subsea structureafter deployment on the seabed and the termination head connected to thesubsea structure at a later date with a substantially horizontalconnection. This type of connection is used predominantly in the NorthSea or other offshore environments where the weather conditions areunpredictable. Deployment on soft seabed will result in sinkage of theconduit termination head, an increase in pull-in loads and reducedvisibility. The operation of pulling the termination across the seabedand into the connection position is typically performed by a toolskidmounted onto an ROV. The ROV provides the electrical or hydraulic power,and buoyancy to allow it to support the toolskid and the terminationhead of the conduit.

[0004] The conduit may be pulled to subsea structures by docking an ROVand toolskid onto the conduit termination head then flying thetermination head to the subsea structure along guide ropes previouslyconnected to the subsea structure, using a winch and the ROV thrusters.The ROV and toolskid then dock on the subsea structure and connect theconduit to the structure.

[0005] On-seabed connection becomes very difficult in deep water. Whilstit is possible to use known, standard ROVs and toolskids up to a depthof 600 m, new designs of ROV and toolskid are required for deployment indeep water because the toolskids must be larger and more powerful, tocope with the increased hydrostatic pressure and higher pull-in andalignment loads. Furthermore, as depth increases, data transmissionbecomes slower and more difficult, and the consequent delay means thatoperation ROV is more difficult to control.

[0006] The main problems in providing conduit connection are related toeither guiding the pipeline to the subsea structure or to the resistanceof the load that occurs in deep water.

[0007] In accordance with the present invention there is provided asubsea connection apparatus comprising: a frame connectable to a subseastructure; docking means for connecting the frame to the subseastructure; conduit handling means positioned on the frame to facilitatethe positioning of a conduit for attachment to a subsea structure; andmeans for docking a subsea tool and/or vehicle onto the frame.

[0008] Preferably, the frame is removably connectable to the subseastructure.

[0009] Preferably, the apparatus is further provided with aligning andguiding means for aligning a conduit while it is handled by the handlingmeans.

[0010] Preferably, the apparatus is further provided with guide meansfor guiding the apparatus to the subsea structure.

[0011] Preferably, the guide means comprises a sleeve having a first endand a second end, the first end being cylindrical in shape and thesecond end being frustoconical in shape. The sleeve is designed toco-operate with docking means located on the subsea structure.

[0012] Optionally, the apparatus is provided with connection means towhich a support cable is fitted. This supports the weight of theapparatus as it is lowered towards the seabed.

[0013] Preferably, the frame has a first end or work area and a secondend or handling area adjacent to the work area.

[0014] Preferably, the work area is adapted to allow an ROV to perform aStroke-in operation on a conduit.

[0015] Preferably, the apparatus is provided with means to increase itsbuoyancy.

[0016] Preferably, the frame is designed to support some or all of themechanical and hydrostatic load associated with connecting a conduit tothe subsea structure.

[0017] Preferably, the frame is provided with a latch, the latch beingconnectable to a conduit to allow the conduit to be supported by theframe in a position adjacent to the frame.

[0018] Embodiments of the present invention will now be described by wayof example only with reference to the accompanying drawings of which:

[0019]FIG. 1 is a perspective view of an embodiment of the presentinvention;

[0020]FIG. 2a is a perspective view of the embodiment of the presentinvention of FIG. 1 being guided towards a subsea structure, FIG. 2b isa side view of the present invention being guided towards a subseastructure and FIG. 2c is a side view of the present invention dockedwith a subsea structure;

[0021]FIGS. 3a to 3 f illustrate the use of the apparatus of the presentinvention for on-seabed conduit connection; and

[0022]FIGS. 4a to 4 f illustrate the use of the apparatus of the presentinvention for catenary pull-in connection.

[0023]FIGS. 5a to 5 d illustrate another embodiment of the subseaconnection apparatus according to the invention. FIGS. 5a and 5 b areplan views of the frame and the termination end of the conduit duringalignment operations. FIG. 5c is a side view of an alignment operation.FIG. 5d is a plan view after the stroke-in of the conduit, i.e. afterthe conduit has been moved into its final position, ready for clampingto the subsea structure.

[0024] The apparatus of the present invention has been designed forconnection to a subsea structure and is capable of bearing some or allof the load associated with connection of a conduit to a subseastructure. In many cases, these loads were previously borne at least inpart by an ROV and/or a toolskid. It allows the simplification of thedesign of the ROV and the toolskid structure so that they can performconnection in deep water. In preferred embodiments, the apparatus of thepresent invention is capable of bearing at least 75% of these loads.

[0025]FIG. 1 is a perspective view of the present invention. Details ofthe frame 5 and the other components of the apparatus will be describedwith reference to FIG. 1.

[0026]FIG. 1 shows the frame 5 which defines a work area 8 arranged, inuse, beside the subsea structure 1. The work area 8, is designed toallow an ROV with a toolskid to perform a Stroke-in operation on aconduit and to facilitate clamp operations such as seal replacement,seal area inspection and cleaning, clamp opening and closing, externalseal testing and clamp removal and replacement. Handling area 9 is alsodefined by the frame 5 and is located remote from the subsea structure,in use, and provides access to the area on the subsea structure 1 wherethe termination head of the pipe will be handled.

[0027] Situated below the handling area 9 are conduit handling means 10,as shown in FIG. 1. The handling means has two handling members, 10 a,each having an internal surface shaped to receive a conduit. Thehandling members are connected together by support means 10 b. Thedocking frame 5 can be provided with aligning and guiding means in orderto be able to align the termination head of the conduit, while it ishandled by the handling means, with the connection hub of the subseastructure. These means allow the guiding of the conduit to a workingposition where the termination head is aligned with the subseastructure's connection point and only a final stroke-in operation has tobe performed. These means can be actuated by the ROV and its toolskid,most of the loads generated by this operation shall be transferreddirectly to frame 5. Interfaces 14, as shown in FIG. 1 are incorporatedin the frame 5 to provide means for docking the toolskid on the frame.The interfaces 14 of the frame also co-operate with docking pins (notshown) of a toolskid which can be connected to the frame 5 to pull aconduit to the subsea structure's connection point or to perform astroke-in operation.

[0028]FIG. 1 shows the frame 5 located on a subsea structure above aconnection point which is located below the central actuation means 12.The connection point is provided with a clamp 3 that contains a centralactuation mechanism 12 and a horizontal leadscrew which allows for avery narrow clamp width of the subsea connection clamp 3.

[0029] In addition, the embodiment of FIG. 1 shows a frame 5 which isprovided with docking means to allow it to be removably connected to thesubsea structure 1. In addition, in this example, the docking means ofthe frame contains guide means in the form of a docking sleeve 6 whichis connectable to a guide pin 7 located upon the subsea structure. Theguide pin 7 has a frustoconical end 8 which co-operates with the firstend 18 of the docking sleeve 6 to connect with the guide pin.

[0030] The guide pin 7 is also provided with pins 13 which co-operatewith slots in the side of the docking sleeve 6 to ensure the correctorientation of the frame 5 with respect to the subsea structure. Thedocking frame 5 may be deployed from the surface on a centralised guidecable 19 extending from a vessel on the surface through the sleeve 6 tothe guide pin 7 on the subsea structure 1 for engagement with the guidepin 7.

[0031]FIGS. 2a-2 c show the apparatus of the present invention beinglowered onto the guide pin 7 situated on the subsea structure. Thefrusto-conical first end 18 of the sleeve 6 provides a larger area intowhich the frusto-conical end 8 of the guide pin 7 can be inserted. Thismakes it easier to connect the apparatus to the subsea structure. Theinterconnection of the guide pins with secondary grooves 110 in thesleeve ensure that the apparatus is correctly orientated with respect tothe subsea structure.

[0032] In addition, the frame 5 may be provided with connection means121 to which a support cable 122 can be attached FIG. 2b. This providessupport to the apparatus as it is lowered towards the seabed and isparticularly useful in cases where the additional weight of the conduittermination head is contained in the handling means 10 when theapparatus and the termination head are being guided to the subseastructure from the vessel as shown in FIGS. 2a-2 c. When the conduit andframe are deployed simultaneously, the conduit is in a working positionso that an ROV and toolskid can perform the stroke-in operation. Theframe with the conduit can be docked on the subsea structure using guidelines deployed from the vessel with the help of an ROV, if necessary.

[0033] The subsea connection apparatus can be deployed separately fromthe subsea structure. Separate deployment is particularly appropriatewhere there are size or weight limitations that preclude deployment ofthe frame and subsea structure together. The apparatus could be deployedon guide cables as described above or using an ROV to push the frameinto the correct position for docking on the subsea structure.

[0034] Further alternatively, the docking frame could be installed bydeploying the docking frame to the seabed in a basket from where it canbe picked up by an ROV and installed on a seabed structure. In this caseadditional ROV Buoyancy may be required to enable the ROV to lift theframe or buoyancy tanks may be incorporated in the apparatus itself. Inaddition, smaller guide pins may be used where the frame is installed byROV.

[0035] Typically, on seabed connection (FIGS. 3a to 3 f) can be achievedusing the apparatus by flying an ROV containing a toolskid 20,connecting pull-in rope 22 to the termination head of a conduit, dockingthe ROV and its toolskid 20 on the frame 5 and pulling the conduit tothe frame using a pull-in module, aligning and guiding the conduit toits working position using the pull-in module and connecting the conduitto a subsea connection using a stroke-in module. During the pull-in andstroke-in phased of the operation, the frame bears most of the weight(typically 75%) associated with the operation.

[0036] In addition, the ROV can perform the pull-in operation and leavethe termination head connected to the frame by means of a hang-off latchand the stroke-in operation can be performed separately.

[0037] In the case of the conduit to be connected during layingoperation, the conduit or termination head may be suspended above theseabed. The ROV and its tool skid connects a cable to the terminationhead of the conduit, and then docks on the frame from where thetermination head is pulled to a position below the frame using thepull-in module of the toolskid and is then connected to the subseastructure using the stroke-in module during the pipe laying operation.

[0038]FIGS. 5a to 5 d show in detail a subsea connection apparatusaccording to the present invention. In particular these figures show indetail the conduit handling means and the guiding and aligning means foraligning the conduit while it is being handled by the handling means.The frame 105 comprises two pivotable outer slide boxes (106 a, 106 b)for accommodating angular displacement and a front section 109. Theseslide boxes are pivotable with respect to front section 109. Cylindersare provided which control the stroke-in distance, the lateral lineardisplacement and the angular displacement of the slide boxes and ensurethe alignment of the conduit in the horizontal plane and a favourableposition of the handling frame as illustrated in FIGS. 5a and 5 b. Theouter slide boxes support a conduit handling swivelling frame 107 whichhandles the termination end of the conduit. A swivel connection 108 withcontrol cylinders 111 allows pivotable movement between the handlingframe and each outer slide box and ensures the alignment in the verticalplane as illustrated in FIG. 5c. The subsea connection apparatus can bedeployed onto the subsea structure using frame docking means asillustrated in the embodiment of FIGS. 2a-2 c. The front frame section109 is linked to the guide sleeve and vertical cylinders can be providedon this part to allow the front frame to move vertically relative to thesubsea structure. The cylinders of the handling means, of the guidingmeans and of the aligning means may be actuated by a ROV docked on thefront frame section 109.

[0039] It is important to note that the apparatus is able to be used foron seabed connection (FIGS. 3a-3 f) for on-structure connection (FIGS.2a-2 c) or for catenary pull-in connection (FIGS. 4a-4 f).

[0040] By transferring most of the operational loads to the apparatus ofthe present invention, it is possible to use standard ROVs and toolskidsfor deepwater conduit connection and it is possible to reduce the sizeof ROV and toolskid used for deep water applications.

[0041] Improvements and modifications may be incorporated herein withoutdeviating from the scope of the invention.

1. A subsea connecting apparatus comprising: a frame connectable to a subsea structure; docking means for connecting the frame to the subsea structure; conduit handling means positioned on the frame to facilitate the positioning of a conduit for attachment to a subsea structure; and means for docking a subsea tool and/or vehicle onto the frame.
 2. A subsea connection apparatus as claimed in claim 1 wherein the frame is removably connectable to the subsea structure.
 3. The apparatus as claimed in claim 1 further provided with aligning and guiding means for aligning a conduit while it is handled by the handling means.
 4. The apparatus as claimed in claim 1 further provided with guide means for guiding the apparatus to the subsea structure.
 5. The apparatus as claimed in claim 2 wherein the guide means comprises a sleeve having a first end and a second end, the first end being cylindrical in shape and the second end being frustoconical in shape.
 6. The apparatus as claimed in claim 1 further provided with connection means to which a support cable is connectable.
 7. Apparatus as claimed in claim 1 wherein the frame has a first end or work area and a second end or handling area adjacent to the work area.
 8. Apparatus as claimed in claim 7 wherein, the work area is adapted to allow an ROV to perform a stroke-in operation on a conduit.
 9. Apparatus as claimed in claim 1 wherein, the apparatus is provided with means to increase its buoyancy.
 10. Apparatus as claimed in claim 1 wherein, the frame is provided with a latch, the latch being connectable to a conduit to allow the conduit to be supported by the frame in a position adjacent to the frame. 